The paper presents the InterOPERA initiative and an EMT‑based study framework to enable interoperability in multi‑terminal, multi‑vendor HVDC grids, covering project scope, demonstrators, functional requirements, and the use of EMTP for interaction and grid‑design studies. The program runs from January 2023 to April 2027 under European funding and coordination by SuperGrid Institute, targeting multi‑vendor HVDC grids to support large‑scale offshore wind integration in Europe. A demonstrator combines building blocks from different vendors—three 2‑GW/525‑kV AC/DC converter stations usable onshore and offshore, four DC switching stations, four power park modules, and a DC grid controller—organized as a three‑terminal base case (with a five‑terminal extension offline) and complemented by a real‑time setup. Functional requirements are structured into sequential control, continuous control, DC grid protection, and AC/DC security and dispatch; examples include onshore DC‑voltage–power droop, DC‑voltage sensitive modes (including limited variants), power‑limiting and DC‑voltage‑limited modes, offshore constant active‑power operation, and DC‑fault ride‑through with fault‑separation zones. EMT is positioned for interaction studies (near steady‑state, energisation/de‑energisation and reconfiguration, withstand, and small‑signal stability) and for HVDC grid‑design studies following a consistent methodology (capability ranges, N‑1 criterion, scenarios and contingencies, modelling assumptions, and DC load‑flow plus dynamic simulations). Using EMTP on the three‑terminal base case, reported study sets cover DC load‑flow and contingency analyses and dynamic responses, with totals including numerous DC load‑flow scenarios (pole and bipole outages), blocking cases with AC faults on the grid side, and DC‑fault events at the DC point of connection, DC switching‑station busbars, and along DC cables. Key messages highlight open‑box models with defined exceptions via tool‑independent DLLs validated in multiple EMT tools, ongoing dry‑run tests, the central role of interface documentation, and real‑time step‑setting trade‑offs.

The paper presents large‑scale electromagnetic transient (EMT) simulation of the French grid, addressing network‑model fidelity and computation‑time challenges, and describing solutions that include an enhanced CIM/EMT interface and sparse solution techniques. The application case covers the entire French grid across 400 kV, 225 kV, 90 kV, and 63 kV, with 25824 three‑phase network nodes, a main system size of 129185, 4725 single‑phase nonlinear saturations, 40 synchronous machines with controls, and 7 HVDC links. The CIM/EMT interface uses planning‑tool data and CIM CGMES files (bus‑branch model), complemented by CSV inputs, and provides model visualization via a graph‑based automatic layout (MSAGL) and a database of substation coordinates with an algorithm to position unknown substations near the closest known coordinates. The sparse EMT solution employs a MANA formulation with discretized companion models, a modified KLU (MKLU) solver, block‑triangular factorization (BTF) for parallelization, fill‑in reduction for LU, and partial refactorization, including per‑BTF‑block updates. Reported performance indicates 47 minutes to simulate 1 second of the full grid, with Ax=b accounting for 93.1% of the time‑domain execution, and speedups up to 5.71×, lowering 1‑second runs to about 8 minutes; next steps include EMTP integration, adding offshore wind parks and manufacturer models, and a parallel co‑simulation platform.

The paper presents the EMT Online Connection Tool—a web‑based platform that automatically integrates generation models with transmission system operator (TSO) network designs, supports remote simulations, enables simultaneous multi‑user access, and preserves confidentiality; the tool is offered to both TSOs and generation owners (GO). Capabilities and workflow include uploading complete grid models and IBR designs, creating a dedicated virtual machine with EMTP for each submission, connecting the generation model to the target bus, executing load‑flow and time‑domain simulations, returning results, and deleting the virtual environment after completion. Additional functionalities include a database management toolbox for exporting designs with metadata, and a grid placeholder device that allows generation owners to connect their models without accessing the full grid representation. Typical TSO and GO actions are summarized to illustrate the operational structure of shared interconnection projects using the tool.

The paper outlines the development and validation of detailed models for Photovoltaic Power Plants using EMTP software to ensure compliance with the Mexican Grid Code. A detailed plant model is initialized to confirm correct operation without power or voltage disturbances, and then exercised through compliance‑oriented scenarios: active power control is evaluated via step and ramp changes to confirm setpoint tracking, while reactive power and power‑factor control modes are exercised to meet strict steady‑state tolerances and response‑time criteria, and voltage control across a 0.95–1.05 p.u. setpoint range. The study also applies frequency‑deviation tests by enabling over‑frequency and under‑frequency modes in the PPC, using selected deadbands and slopes while holding active power at 0.8 p.u. during the procedure to evaluate primary frequency regulation performance.

The paper presents an EMT‑based assessment of a radial transmission network in the Gaspésie region, where wind generation penetration exceeds local demand and creates weak‑grid conditions. Motivated by the limits of phasor‑domain transient (PDT) tools in representing fast inverter‑based resource (IBR) dynamics, the study uses EMTP simulations to validate the operational active‑power transfer limit of the main transmission corridor. The modeled system includes over 2,250 MW of wind generation, HVDC links, series‑compensated lines, and OEM wind farm black‑box models in accordance with CIGRÉ TB‑881 guidelines. Contingency analyses—including three‑phase and phase‑to‑ground faults—reveal significant discrepancies between EMTP and PDT results, with EMTP predicting much higher wind‑generation losses and stronger voltage‑instability phenomena. The findings demonstrate that EMT simulations are essential to accurately capture IBR control interactions, assess transient voltage and frequency stability, and validate safe operating limits in weak‑grid environments with high renewable penetration.

The paper presents an analysis of reactive power regulation issues in wind farms operating under weak‑grid conditions, as required by the Mexican Grid Code. Data‑driven simulations using real measurements demonstrate that, although the wind farm generates significant reactive power oscillations, the major voltage disturbance originates from an external grid event rather than from the plant itself. The study shows that appropriate tuning of the wind farm control system can effectively mitigate voltage oscillations, whereas improper tuning may exacerbate system instability and lead to non‑compliance with regulatory requirements. To address these challenges, the work develops and validates detailed modulation and control schemes for MMC‑based STATCOMs, including automated submodule generation and advanced reactive power control. Simulation results confirm their ability to provide dynamic compensation and support regulatory compliance, demonstrating the feasibility and effectiveness of integrating STATCOMs in renewable‑rich weak‑grid environments.

The paper presents simulations of a new test on HVDC cables involving a superimposed impulse voltage test, where the EMTP model was validated against real measurements taken in an HV laboratory. Additionally, simulations of very slow temporary overvoltage (TOV) on HVDC cable are shown, aiming to verify whether the existing impulse generator provides sufficient energy, given the challenge of prolonged test duration. Another similar simulation example illustrates a combined heat and basic impulse level (BIL) test, used to assess the energy capability of the impulse generator. Beyond its application in validating new test requirements and configurations in the HV lab, EMTP can also be used for the development of novel testing methods, such as the low-frequency signal injection method for earth-fault detection, where the simulation results were also validated with real-world measurements.

This tool ensures your Inverter-Based Resource (IBR) model is interconnection-ready. It is an advanced automation module built in EMTP®. Developed for Generation Owners (GOs), system operators (ISO, TSO), and consultants, E-Interconnect drastically simplifies the complex, time-consuming process of running Model Quality Tests (MQT) and conformity assessments required for grid connection. More information here: https://www.emtp.com/products/modules/e-interconnect – Willy Nzale, Henry Gras

EMTP® recorded the 26th of November 2025, showing the newly released E-interconnect tool.

Faults within a transmission system can greatly impact the capability for power transfer. Isolating a fault by removing the line from service can further diminish the power transfer capacity, compromising the system`s stability margin. Single-phase-to-ground faults, which are the most frequent, can be effectively isolated by taking only the affected phase out of service, while keeping the remaining two phases active. This approach, referred to as single-pole switching (SPS), permits the line to carry two-thirds of its power and preserve synchronization between the sources at both ends of the line, However, it presents distinct challenges. In a long line, a small AC current can still sustain even after the breakers open. This current is called the secondary arc current and it is due to electromagnetic coupling between the phase conductors. If the breaker pole is reclosed before this current extinguishes, the fault will reoccur, leading to unsuccessful reclosure. The aim of this work is to identify the key factors that significantly influence the secondary arc current and to evaluate different methods to reduce its amplitude. For successful reclosure, the circuit breaker`s dead time must be longer than the secondary arc`s extinction time. This study models the secondary arc using the EMTP program to simulate its interaction with the transmission system and estimate the necessary dead time for the circuit breaker. The study analyzes the self-extinguishment of the secondary arc by monitoring its magnitude and the recovery voltage using EMTP. It concludes with recommendations for reducing the secondary arc current and determining the minimum dead time required for the successful reclosure of a 380KV transmission line.

The implementation of distributed generation sources with islanding microgrid capabilities can introduce new challenges for engineers integrating new large generators to existing power systems. The generator interconnection transformer winding configuration and the generator winding pitch greatly impacts the flow of circulating currents and can result in unexpected generator heating, as well as high grounding resistor operating temperatures. This presentation presents a case study of the flow of 3rd order harmonic currents in a microgrid power system, and how EMTP was used to design equipment modifications necessary to reduce the current. A review of generators and how they can lead to 3rd order harmonic current generatio, along with additional options for correcting this condition will be presented.

Since 2022, the National Electric Coordinator in Chile has requested standardization of the dynamic models of the power plants or parks connected to the National Electrical System (SEN). As a company (EEMT), we have participated in the development of dynamic models for various wind and photovoltaic parks, carrying out a series of EMT homologations, both for equivalent and complete models. This involves analyzing their operation and validating them through records. Once this process is completed, it is possible to conduct tests and systemic verifications on the model, performing different short circuits and analyzing the LVRT. Thanks to the development and homologations of these models, in their complete and equivalent stages, different analyses can be carried out where electromagnetic phenomena exist for complete models, while with the equivalent models analyses can be carried out in a delimited area, generating faults and comparing them with real cases that have occurred. Within the framework of this conference, EEMT wants to present what the development of the homologation of these models has meant, the results that have been obtained in their different stages, and the usage that can be given to them for the performance of different analyses. On the other hand, as a consulting firm, we have been developing our own model of the Chilean National Electrical System based on various studies and based on the experience we have acquired as a leading consulting in EMT models. With the progress of homologations and the development of EMT models, it is expected that in the future there will be a systemic Database of the SEN that contains a greater number of aggregated models and that reliably allows for a large scale systemic analysis, such as, failures in the 500 kV transmission line, among other phenomena.

In this hydroelectric generation project, connection is established in a 500 kV system, which includes series compensation. A comprehensive TRV analysis was conducted to evaluate the existing circuit breakers. Based on this analysis, it was determined that implementing opening resistors is necessary to mitigate the adverse effects of TRV and ensure compliance with Peruvian electrical regulations.

This presentation will focus on a specific issue of bipolar HVDC lines with a dedicated metallic return (DMR). DMR is insulated to a lower level than the pole and its insulators are shorter. One event, for example, pole-to-ground-fault will cause a fault on both the pole insulation and the DMR insulation simultaneously because the DMR insulation fault will be supported by the DC current and will turn into a DC arc. To ensure independent pole operation, these types of events should be avoided or, if the DMR does flashover, to extinguish the fault as soon as possible. This is phenomena are presented and how different solutions are tested with EMTP software to protect the DMR.

This is a presentation on lightning overvoltage analyses for a 500/220 kV substation. Highlights: An interesting application case where the electrical distance between the surge arrester and transformer was quite long, requiring us to check the adequacy of the surge arrester. Proper selection of lightning parameters in line with CIGRE TB063 (updated in 2021). We can provide some easy-to-use recommendations for lightning waveform modeling. Modeling of substation apparatus, including some brief guidelines and critical points not to miss.

Shunt compensation reactors, deployed in long AC transmission lines, serve to mitigate overvoltages induced by capacitive charging under light load conditions. However, these reactors can introduce operational challenges, notably sustained overvoltages due to zero sequence resonance. Such resonance occurs in unbalanced conditions, often stemming from circuit breaker malfunctions that result in one- or two-phase disconnections. The zero-sequence resonance is triggered between shunt reactors and phase capacitance in disconnected phases. The overvoltage caused by this resonance can lead to equipment damage. The overvoltage caused by this resonance can lead to equipment damage.
The presentation will cover:
• Zero Sequence Resonance: Background on the phenomenon and resulting sustained overvoltages.

This presentation shows the acceptance tests performed on a wind power plant modeled using the WECC model. The plant cosistes of 121 turbines, each with a capacity of 0.85 MW, operating at 60 Hz. These turbines are connected to the 34.5 kV medium voltage collector system via 121 step-up transformers. The wind power plant is linked to the 320 kV network through a 230/34.5 kV 125 MVA main facility transformer. Other network components, such as collector cables and wind turbine step-up transformers, have also been represented by their equivalents. The model was developed and validated using two commercial tools – EMTP® and PSS®E. Simulations and analysis were performed to validate a group of acceptance tests required by the local utility. This presentation will focus on the modelling process, analysis and results obtained using EMTP®. The results obtained from the EMTP® and PSS®E are compared and discussed.

This presentation examines the impact of high DER penetration, particularly PV systems, on EPDS protection reliability. Instead of concentrating DERs in specific nodes, they are distributed along an unbalanced feeder with single-phase and three-phase PV systems. Various fault types, including impedance faults, were analyzed using the IEEE 34-node test feeder in EMTP-RV. Three scenarios were considered: (i) without DERs, (ii) 50% DER penetration with protection set by rated load, and (iii) 50% DER penetration with protection set by conductor capacity. Results showed reduced feeder relay currents for three-phase and phase-to-phase faults and significant decreases for phase-to-ground faults with impedance, leading to relay blindness and delayed protection operation. These insights support utilities in adapting EPDS protection systems for DER integration.

In this presentation three single-core cables with 630 mm2 copper conductors and lead sheathed cores, being in trefoil touching formation, are simulated through EMTP® and evaluated against experimental measurements. Both solid- and single-point sheath bonding configurations are considered. The standing voltages and circulating currents induced in the metallic sheaths are measured and compared against EMTP®. Positive-sequence impedance and loss results are also considered. As demonstrated, significantly better agreement between theoretical and experimental results occur when proximity effects are considered in EMTP®.

This chapter presents some analysis of the modeling techniques used to evaluate the effects of electromagnetic interference phenomena that could occur when metallic pipelines are placed close to high-voltage power lines. The electric and magnetic fields produced by overhead power lines could perturb the normal operation of the metallic pipelines through induced currents and voltages. These perturbations could be dangerous for both pipeline operating personnel (as electrical hazard) and pipeline structural integrity (due to accelerated electrochemical corrosion phenomena). The chapter depicts the electromagnetic coupling mechanisms behind the abovementioned interference phenomena and how the induced voltages could be evaluated. A parametric analysis is showcased to highlight the influence of various geometrical and electrical parameters.

The Delta-connected STATCOM is regarded as the most advantageous topology for STATCOMs based on the Modular Multilevel Converter (MMC) technology. Embedding energy storage devices into the MMCs has gained significant research interest in recent years. This presentation focuses on modeling of MMC-based Delta-STATCOMs with embedded energy storage. A flexible modeling approach is proposed, which allows easy interfacing of various converter models with various energy storage device models. Four commonly used types of MMC models are applied to STATCOM modeling: detailed, detailed equivalent, arm equivalent, and average value. Supercapacitors and batteries are used as energy storage devices. Dynamic performances of the models are compared in transient simulation cases using EMTP.

EHV cables have higher capacitance and a larger current, which increases the possibility of overvoltage occurrences during the charging. A 400kV EHV cable experienced a long-duration overvoltage incident that damaged the Lightning Arrestor. The incident was analyzed using EMTP®, and mitigation methods for cable charging were proposed. The EMTP simulation and site relay measurements matched closely. The presentation will share the analysis results and mitigation methods.

Battery technology and power electronic converters have facilitated the widespread use of Electric Vehicles (EVs), resulting in reduced rotational inertia and frequency stability of the power system. To address this issue, grid frequency support must be provided through various methods, including the regulation of power exchange between the grid and grid-tied inverter. Virtual inertia can be obtained from the energy stored in the DC link capacitors of the grid-tied VSC and the battery charging points. Coordinated droop control strategies from the VSC and EV charging ports can provide frequency support to the grid during disturbances. This session will discuss the use of EMTP® simulations to develop coordinated droop control strategies for mitigating frequency stability issues.

This presentation will focus on a specific issue of bipolar HVDC lines with a dedicated metallic return (DMR). DMR is insulated to a lower level than the pole and its insulators are shorter. One event, for example, pole-to-ground-fault will cause a fault on both the pole insulation and the DMR insulation simultaneously because the DMR insulation fault will be supported by the DC current and will turn into a DC arc. To ensure independent pole operation, these types of events should be avoided or, if the DMR does flashover, to extinguish the fault as soon as possible. This is phenomena are presented and how different solutions are tested with EMTP software to protect the DMR.

In this work, the standard model for wind power generation systems based on the international standard IEC 61400-27-1 (Edition 2.0, 2020) was implemented in EMTP®. Its validation has been carried out in a test system with respect to a validated RMS model of a wind farm in Chile.